This invention relates to a variable edge rotor blade and more particularly to such a variable edge blade in which the actuator is contained in the blade and operates independently of the hub.
Army rotorcraft are being called upon to operate in much more demanding environments than in the past, particularly in areas of nap-of-the earth (NOE), deep-penetration, and air-to-air combat. Highly maneuverable, agile, and survivable rotorcraft demand greater aerodynamic capability from the rotor system. Aerodynamic performance is currently limited, to a great degree, by the low maximum lift coefficient of conventional rotor blade airfoils, and conflicting airfoil shape requirements of the advancing and retreating blade at high speed. Retreating blades optimally have round large radius high-cambered leading edge type airfoils to achieve a high lift coefficient. In contrast, advancing blades optimally have thin, low-cambered airfoils to avoid high shock loss and drag penalties.
One attempt to solve this problem resulted in an airfoil with a fixed camber at a compromise angle at the leading edge of the airfoil. The fixed camber at a compromise angle provides a small benefit for advancing blades, but proved to be a hindrance for retreating blades.
Another attempt involved controlling the flaps of a blade through a complex system which includes a swash plate and an axle which carries, for each blade, an articulation connected to a system of rods which comprises a crank-arm hinged on a sealer in contact with the swash plate. The crank-arm actuates a counter member which causes a rod connected to a flap to pivot. However, such a complex system which is connected to the hub adds a significant amount of weight, and increases aerodynamic drag. Additionally, the number of components necessary in such a complex system from the hub to the flap renders the system susceptible to reliability and maintenance concerns.
It is therefore an object of this invention to provide a rotorcraft with an improved variable edge rotor blade.
It is a further object of this invention to provide an improved variable edge rotor blade in which the edge angle can be varied as the blade rotates to increase the stall angle of attack, lift, speed, payload, and maneuverability.
It is a further object of this invention to provide an improved variable edge rotor blade of less complexity and lighter in weight.
It is a further object of this invention to provide such an improved variable edge rotor blade in which the variable edge actuator is contained in the blade and operates independently of the hub.
It is a further object of this invention to provide such an improved variable edge rotor blade which is simple in design, which uses fewer components, and is operable at higher g forces.
It is a further object of this invention to provide such an improved variable edge rotor blade which contributes to reduced fuel consumption, higher cruise speeds, reduced vibration, and improved component life and maintenance.
The invention results from the realization that a simpler variable edge rotor blade with increased performance can be achieved with an actuator that operates independently of the hub and is contained in the blade fixed to the airfoil section proximate the movable edge section and coupled to the movable edge section for oscillating it between greater and lesser lift positions.
This invention features a variable edge rotor blade adapted to be driven by the rotor hub including an airfoil section and a movable edge section coupled to the airfoil section. An actuator operating independently of the hub, disposed in the blade proximate the movable edge section and fixed to the airfoil section, is coupled to the movable edge section for oscillating the movable edge section between an increased lift and decreased lift position.
In a preferred embodiment the movable edge section may include a deflectable contour member connected with the airfoil section. The movable edge section may include an edge element pivotably connected to the airfoil section. The edge element may include first and second ends, the first end being pivotably connected to the airfoil section and the second end abutting the airfoil section. The second end may alternately confront and recede from the airfoil section creating a gap.
The movable edge section may include a contour member conforming to the airfoil section and connected to one of the airfoil section and the movable edge section. The contour member may be deflectable and coupled to at least one of the airfoil and movable edge sections. The actuator device may include a reciprocating member coupled to the movable edge section and a motor for driving the reciprocating member.
The actuator device may include a magnet on one of the movable edge section and airfoil section and an electromagnetic coil coupled to the other and an alternating power source for energizing the coil to oscillate the movable edge section. The movable edge section may be the leading edge of the rotor blade. The deflectable contour member may be stretchable. The coil may be fixed to the airfoil section and the magnet fixed to the movable edge section. The coil may be fixed to the movable edge section and the magnet may be fixed to the airfoil section. The coil may be flexible and fixed to the airfoil section and the movable edge section as well. The gap may be filled with a flexible material. The edge element may be pivotably connected to the airfoil section by a torsion bar. The reciprocating member may be hinged to the movable edge section or it may be fixed to the movable edge section.
The movable edge section may include a deflectable contour member coupled to the airfoil section, and the actuator device may include a shaper bar between the airfoil section and the contour member and a mechanism coupled to the shaper bar for moving the shaper bar to change the shape of the contour member.
This invention also features a variable edge rotor blade adjusted to be driven by a rotor hub including an airfoil section and a movable edge section including an edge element having a first end and a second end and coupled to said airfoil section. The first end is pivotably connected to the airfoil section and the second end abuts the airfoil section. The movable edge section also includes a contour member conforming to the airfoil section and the edge element and connected to either the airfoil section or the edge element, proximate the second end of the edge element. There is an actuator device operating independently of the hub, disposed in the blade proximate the edge element, fixed to the airfoil section and coupled to the edge element for oscillating the edge element between an increased lift and decreased lift position.
This invention also features a variable edge rotor blade adjusted to be driven by a rotor hub including an airfoil section and a movable edge section including an edge element having a first end and a second end and coupled to the airfoil section. The first end of the movable edge section is pivotably connected to the airfoil section and the second end abuts the airfoil section. The movable edge section also includes a contour member conforming to the airfoil section and the edge element, the contour member connected to the airfoil section. An actuator device operates independently of the hub and is disposed in the blade proximate the movable edge section, fixed to the airfoil section and coupled to the edge element for oscillating the edge element between an increased lift and decreased lift position.
This invention also features a variable edge rotor blade adapted to be driven by the rotor hub including an airfoil section and a movable edge section coupled to the airfoil section including a deflectable contour member coupled to the airfoil section. An actuator device operates independently of the hub and is disposed in the blade proximate the movable edge section, fixed to the airfoil section and coupled to the movable edge section for oscillating the movable edge section between an increased lift and decreased lift position. The actuator device includes a shaper bar between the airfoil section and the contour member and a mechanism coupled to the shaper bar for moving the shaper bar to change the shape of the contour member.